Hi blizz. I don't have asthma, but I do take the dreaded prednisone for an arthritis condition. I've been assured that it's perfectly safe in pregnancy and doesn't cross the placenta. It's different to the steroids used to develop a baby's lungs when they are in danger of a premature birth. The drug is also used in some cases to help prevent miscarriages, so you can take it during pregnancy with absolute confidence that you are not doing great harm to your baby.

Hope this helps ease your mind.

BW